Are Large Sulfur Isotope Variations Biosignatures in an Ancient, Impact-Induced Hydrothermal Mars Analog?
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View abstract on PubMed
Summary
This summary is machine-generated.Sulfur stable isotope ratios (δ³⁴S) in impact crater lakes may not reliably indicate life. Earth-based studies of the Nördlinger Ries crater suggest abiotic processes can create large δ³⁴S variations, challenging their use as biosignatures.
Area Of Science
- Astrobiology
- Geochemistry
- Paleontology
Background
- Sulfur stable isotope ratios (δ³⁴S) are debated as biosignatures in impact crater paleolakes.
- Martian δ³⁴S data from Gale Crater show large variations attributed to abiotic processes.
- Earth-based studies often interpret δ³⁴S fractionations >21‰ as biological, including in analog impact crater lakes.
Purpose Of The Study
- To investigate whether δ³⁴S properties in the Nördlinger Ries impact crater define a biosignature.
- To analyze lithologies from a terrestrial analog impact crater lake environment.
Main Methods
- Analysis of δ³⁴S, total organic carbon (TOC) wt%, and scanning electron microscope (SEM) imaging.
- Focus on hydrothermally altered impact breccias and sedimentary lake-fill sequences.
- Examination of multiple lithologies from the Miocene Ries impact crater.
Main Results
- Observed differences in δ³⁴S between host lithologies at the Ries crater.
- Potential causes for δ³⁴S variations include thermochemical sulfate reduction, microbial sulfate reduction, or hydrothermal equilibrium fractionation.
- Assertions of biogenicity based solely on δ³⁴S variations >21‰ are considered tenuous.
Conclusions
- The use of δ³⁴S as a sole biosignature in impact crater lakes is discouraged.
- Independent checks incorporating geologic, biogeochemical, and textural context are crucial.
- Alternative hypotheses must be comprehensively acknowledged when interpreting δ³⁴S data.
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